High-frequency receiver and portable device using the same

ABSTRACT

A high-frequency receiver and a portable device using the same receiver are proposed for reducing power consumption. Image interference determiner ( 44 ) determines whether or not image interference exists at the present position in a desirable channel to be received, which channel is obtained by a receiving section ( 39 ) or a GPS receiver ( 43 ). Power supply control circuit ( 47 ) switches mixer ( 49 ) from an image rejection mixer to a double balance mixer when determiner ( 44 ) determines no image interference involves. This mechanism allows mixer ( 49 ) to work as the double balance mixer circuit during the reception of channels free from image interference, so that a mixer consuming less power is achievable. When mixer ( 49 ) works as the image rejection mixer circuit, image interference can be reduced.

FIELD OF THE INVENTION

The present invention relates to high-frequency receivers to be used intuners for receiving television signals, and it also relates to portabledevices using the same receivers.

BACKGROUND OF THE INVENTION

FIG. 14 shows a block diagram illustrating a conventional high-frequencyreceiver. In FIG. 14, input terminal 1 receives high-frequency signalshaving frequencies ranging from 55.25 MHz to 801.25 MHz. Input terminal1 connects to single-tuned filter 2 of which tuned frequency ranges from367.25 MHz to 801.25 MHz (UHF broadcasting band). The tuned frequency iscontrolled by a tuning voltage supplied to frequency variable terminal 2a.

High-frequency amplifier 3 receives an output signal from single-tunedfilter 2, amplifies signals of UHF band, and outputs the resultantsignals to double-tuned filer 4. Filter 4 includes two variablecapacitance diodes, and tuned frequencies are controlled by a tuningvoltage supplied to frequency variable terminal 4 a.

Mixer 5 receives an output signal from double-tuned filter 4 at itsfirst input terminal 5 f, and receives an output signal from localoscillator 6 at its second input terminal 5 s via frequency divider 7.Mixer 5 mixes UHF band signals having undergone double-tuned filter 4with oscillating signals supplied from local oscillator 6, and convertsthe resultant signals into intermediate frequency signals of 45.75 MHz.

Intermediate frequency filter 8 connects to an output terminal of mixer5, and attenuates undesired signals in occupied frequency bandwidth of 6MHz. Output signals from intermediate frequency filter 8 is supplied tooutput terminal 9 via intermediate frequency amplifier 25.

UHF signal receiving section 10 is thus formed of single-tuned filter 2,high-frequency amplifier 3, double-tuned filter 4, mixer 5 andintermediate frequency filter 8.

The high frequency signal supplied to input terminal 1 is also suppliedto VHF signal receiving section 11, which receives signals havingfrequencies ranging from 55.25 MHz to 361.25 MHz (VHF broadcastingband). VHF signal receiving section 11 is formed of single-tune filter12, high-frequency amplifier 13, double-tuned filter 14 and mixer 15.

Single-tuned filer 12 includes one variable capacitance diode, and itstuned frequency is controlled by a tuning voltage supplied to frequencyvariable terminal 12 a. High-frequency amplifier 13 connects to anoutput terminal of single-tuned filter 12, and amplifies VHF bandsignals. Double-tuned filter 14 connects to an output terminal ofhigh-frequency amplifier 13, and it has two variable capacitance diodes.Its tuned frequency is controlled by a tuning voltage supplied tofrequency variable terminal 14 a.

Image rejection mixer (IRM) 15 is formed of two mixers and two phaseshifters. IRM 15 receives an output signal from double-tuned filter 14at its first input terminal 15 f, and receives an output signal fromlocal oscillator 6 via frequency divider 16 at its second input terminal15 s. IRM 15 mixes the VHF band signals having undergone double-tunedfilter 14 with oscillating signals supplied from local oscillator 6, andconverts the mixed signals into signals having intermediate frequency of45.75 MHz. IRM 15 supplies the resultant signals to intermediate filter8 via lead-wire 26.

Local oscillator 6 includes OSC 17 of which input terminals 17 a and 17b are connected to tuning section 18. Tuning section 18 is formed ofseries-connected unit 21 formed of variable capacitance diode 19 andcapacitor 20 connected in series, and inductor 22 connected in parallelwith unit 21.

Phase locked loop (PLL) circuit 23 placed approx. at the center of FIG.14 receives output signals from OSC 17 at its input terminal, andsupplies a tuning voltage from its output terminal 23 a to variablecapacitance diode 19 of tuning section 18. The tuning voltage is alsosupplied to respective variable capacitance diodes of single-tunedfilter 2, double-tuned filter 4, single-tuned filter 12, anddouble-tuned filter 14. The tuning voltage thus controls oscillatingfrequency of local oscillator 6 as well as respective tuned frequenciesof single-tuned filters 2, 12, double-tuned filters 4, 14.

Meanwhile, the prior art related to the present invention are disclosed,e.g. in Japanese Patent Unexamined Publication No. 2000-295539,2002-118795, and H01-265688.

The conventional high-frequency receiver discussed above; however, mustinclude two mixers and two phase shifters regardless of whether or notthey receive signals having frequencies interfering with images in areceived channel. Thus the receivers are required to consume less power,and it is hard particularly for battery-operated portable devices toachieve this requirement.

The present invention thus aims to provide high-frequency receiversconsuming less power and portable devices using the same receivers.

SUMMARY OF THE INVENTION

The present invention determines whether or not image interferenceexists in a desirable channel to be received, and if the imageinterference is acknowledged, a power control circuit turns off a partof IRM circuit which is one of the mixers. This turn-off changes themixer, which has been working as an IRM circuit, to work as a doublebalance mixer (DBM) circuit.

An image interference determiner detects and determines imageinterference in a desirable channel at the present position, and thepower control circuit makes the mixer work as the DBM circuit when thedeterminer determines that no image interference exists.

The foregoing mechanism allows the mixer to work as the DBM circuit whenthe receiver of the present invention receives a channel free from imageinterference, so that the mixer consuming less power is obtainable. Whenthe mixer works as the IRM circuit, it can reduce image interference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram illustrating a portable receiver inaccordance with a first exemplary embodiment of the present invention.

FIG. 2 shows a block diagram illustrating a high-frequency receiver inaccordance with the first exemplary embodiment of the present invention.

FIG. 3 shows a circuit diagram of a tuned filter which receives UHF bandin accordance with the first exemplary embodiment of the presentinvention.

FIG. 4 shows a circuit diagram of a tuned filter which receives VHF bandin accordance with the first exemplary embodiment of the presentinvention.

FIG. 5 shows a block diagram detailing a frequency divider and a mixerin accordance with the first exemplary embodiment of the presentinvention.

FIG. 6A shows timing charts of signals in accordance with the firstexemplary embodiment of the present invention.

FIG. 6B shows operations of respective circuits and statuses of switchesduring the receptions of respective frequency bands in accordance withthe first exemplary embodiment of the present invention.

FIG. 7A shows a block diagram illustrating a frequency divider and amixer in accordance with a second exemplary embodiment of the presentinvention.

FIG. 7B shows operations of respective circuits and statuses of switchesduring the receptions of respective frequency bands in accordance withthe second exemplary embodiment of the present invention.

FIG. 8 shows a block diagram illustrating a high-frequency receiver inaccordance with a third exemplary embodiment of the present invention.

FIG. 9A shows a block diagram detailing a frequency divider and a mixerin accordance with the third exemplary embodiment of the presentinvention.

FIG. 9B shows operations of respective circuits and statuses of switchesduring the receptions of respective frequency bands in accordance withthe third exemplary embodiment of the present invention.

FIG. 10 shows a block diagram illustrating a high-frequency receiver inaccordance with a fourth exemplary embodiment of the present invention.

FIG. 11A shows a block diagram detailing a frequency divider and a mixerin accordance with the fourth exemplary embodiment of the presentinvention.

FIG. 11B shows operations of respective circuits and statuses ofswitches during the receptions of respective frequency bands inaccordance with the fourth exemplary embodiment of the presentinvention.

FIG. 12 shows timing charts of signals in accordance with the fourthexemplary embodiment of the present invention.

FIG. 13A shows a block diagram detailing a frequency divider and a mixerin accordance with a fifth exemplary embodiment of the presentinvention.

FIG. 13B shows operations of respective circuits and statuses ofswitches during the receptions of respective frequency bands inaccordance with the fifth exemplary embodiment of the present invention.

FIG. 14 shows a block diagram illustrating a conventional high-frequencyreceiver.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Exemplary Embodiment 1

The first exemplary embodiment of the present invention is demonstratedhereinafter with reference to accompanying drawings. FIG. 1 shows ablock diagram illustrating a portable high-frequency receiver. Antenna30 for receiving television (TV) broadcastings receives, e.g. VHFbroadcasting band as a first frequency band and UHF broadcasting band asa second frequency band. The frequencies of those bands range fromapprox. 55.25 MHz to 801.25 MHz. Antenna 30 connects to high-frequencyreceiver 31 at its output terminal. Receiver 31 selects signals of adesirable channel from among the received high-frequency signals, andoutputs signals converted into an intermediate frequency of 45.75 MHz.

Demodulator 32 demodulates the intermediate frequency signals suppliedfrom receiver 31. Decoder 33 receives output signals from demodulator 32carries out vitebi-correction and reed-solomon correction, and thesignals having undergone those corrections are output to speaker 35 orliquid crystal display 36 via signal processor 34.

Cellular phone antenna 37 receives cellular telephone signals having afrequency of approx. 800 MHz, and duplexer 38 receives output signalsfrom antenna 37. Signals at an output terminal of duplexer 38 areconverted into signal data via receiving section 39, then the convertedsignals are supplied to signal processor 34. Receiving section 39 is oneof positional data obtaining means.

Audio signals supplied to microphone 40 are converted into digitalsignals by signal processor 34, and sent to transmitting section 41,where the audio signals are converted into telephone signals. Thecellular telephone signals are radiated into the air from antenna 37 viaduplexer 38 for propagation.

GPS antenna 42 receives signals, which are then supplied to GPS receiver43, and receiver 43 outputs information about the present position ofthe portable receiver. GPS receiver 43 is used as another one of thepositional data obtaining means.

Image interference determiner 44 receives output signals from receivingsection 39 at its first input terminal 44 f, and receives output signalsfrom GPS receiver 43 as well as output signals from received channeldata generator 45 at its second input terminal 44 s respectively. Imageinterference determiner 44 connects to memory 46 which has stored a datatable of receivable channel frequencies corresponding to position data.Output terminal 44 t of determiner 44 connects to power supplycontroller 47 disposed in high-frequency receiver 31. Controller 47connects to frequency divider 48 and mixer 49 of receiver 31, and turnson or off the power supplies of those elements. While the power suppliesof divider 48 and mixer 49 are turned on (hereinafter this status isreferred to as a regular mode), mixer 49 works as an image rejectionmixer (IRM). On the other hand, while those power supplies are turnedoff (hereinafter referred to as a power-saving mode), mixer 49 works asa double balance mixer (DBM). In other words, mixer 49 has twofunctions, i.e. the IRM and the DBM.

In this first exemplary embodiment, receiving section 39 also suppliesits output signals to memory 46, so that use of a cellular phone allowsobtaining a frequency table of channels receivable at the presentposition via the Internet Web. As a result, in receivable channels, thereceiver of the present invention can deal with changes caused by anadditional broadcasting station.

Image interference generated in a high-frequency receiver that receiveswide-band high-frequency signals such as TV broadcasting is describedhereinafter. One of VHF broadcasting stations in Japan is taken as anexample, that is Channel 4 using approx. 173 MHz. Since the intermediatefrequency signal in this first embodiment uses 45.75 MHz, the frequencythat generates image interference is approx. 219 MHz (the same frequencyof Channel 12 of VHF in Japan). In other words, in an area where bothChannel 4 and Channel 12 are receivable, when Channel 4 is received, thesignals of Channel 12 interfere with the image. On the other hand, in anarea where Channel 12 is not receivable, reception of Channel 4 does notinvolve image interference.

Next, an operation of high-frequency receiver 31 is demonstratedhereinafter. First, image interference determiner 44 obtains data ofpresent position from receiving section 39 or GPS receiver 43, andretrieves data of receivable channel frequencies corresponding to thepresent position from the table stored in memory 46. On the other hand,when an operator of a portable receiver inputs a desirable channelthrough a keyboard (not shown), receivable channel data generator 46generates the data of a desirable channel to be received, and this datais supplied to PLL circuit 78 and image interference determiner 44.Determiner 44 determines whether or not any channels among the desirablechannels to be received at the present position involve imageinterference.

When determiner 44 determines that there is no channel which involvesimage interference to the receivable TV broadcasting channels at thepresent position, the receiver receives the broadcasting in the powersaving mode. At this time, the power supplies of frequency divider 48and mixer 49 are turned off, and mixer 49 works as the DBM, so that thehigh-frequency receiver consumes less power. On the other hand, ifdeterminer 44 determines that there is a channel involving imageinterference to the TV channels receivable at the present position, thereceiver receives the broadcasting in the regular mode.

In FIG. 1, signal quality determiner 50 is disposed between the outputside of decoder 33 and the input side of power supply controller 47.Signal quality determiner 50 determines a bit-error rate of a receivedsignal. When the bit-error rate of the signal supplied from decoder 33becomes not less than 0.0002, determiner 50 sends a signal, which turnson parts of divider 48 and mixer 49, to power supply controller 47.

For instance, during the power-saving mode operation, when signalquality determiner 50 finds the bit-error rate not less than 0.0002,power supply controller 47 turns on frequency divider 48 and mixer 49 sothat the operation is changed to the regular mode. Mixer 49 thus worksas the IRM, and as a result, the bit-error rate adversely influenced byimage interference can be improved.

Next, high-frequency receiver 31 in accordance with the first embodimentis demonstrated hereinafter with reference to FIG. 2, which shows ablock diagram illustrating receiver 31. In FIG. 2, input terminal 51 isconnected to antenna 30 shown in FIG. 1. Single tuned filter 52 includesa variable capacitance diode and connects to input terminal 51. Filter52 controls tuned frequencies ranging from 367.25 MHz to 801.25 MHz (UHFbroadcasting band). The tuned frequencies are controlled by a tuningvoltage supplied to frequency variable terminal 52 a.

High-frequency amplifier 53 connects to single-tuned filter, andamplifies signals of UHF broadcasting band. Amplifier 53 connects todouble-tuned filter 54 at its output terminal. Filter 54 includes atleast two variable capacitance diodes and its tuned frequencies arecontrolled by a tuning voltage supplied to frequency variable terminal54 a.

First input terminal 55 f of mixer 55 connects to output terminal 54 bof double-tuned filter 54, and second input terminal 55 s receivesoutput signals from local oscillator 56 via frequency divider 48. Mixer55 also works as the DBM previously discussed, and mixes UHF bandsignals having undergone filter 54 with oscillating signals suppliedfrom local oscillator 56, and converts the mixed signals intointermediate frequency signals of 45.75 MHz.

Output signals from mixer 55 are taken out from output terminal 79, andthey are supplied to intermediate frequency filter 58, which attenuatesundesired signals in occupied frequency band of 6 MHz. Output signalsfrom filter 58 are supplied to output terminal 59 via intermediatefrequency amplifier 25.

UHF signal receiving section 60 placed at the upper portion of FIG. 2 isformed of single-tuned filter 52, high-frequency amplifier 53,double-tuned filter 54, mixer 55 and intermediate frequency filter 58.

VHF signal receiving section 61 placed at the lower portion of FIG. 2connects to single-tuned filter 62 at its input terminal 51, andhigh-frequency amplifier 63, double-tuned filter 62, mixer 49 areconnected in this order after filter 62 onward. VHF signal receivingsection 61 receives input signals supplied from input terminal 51, sothat it receives VHF broadcasting signals having frequencies rangingfrom 55.25 MHz to 361.25 MHz.

Single-tuned filter 62 includes at least one variable capacitance diode,and its tuned frequency is controlled by a tuning voltage supplied tofrequency variable terminal 62 a. High-frequency amplifier 63 receivesoutput signals from single-tuned filter 62, and amplifies the signals inVHF broadcasting band.

Double-tuned filter 64 receives output signals from amplifier 63. Filter64 includes at least two variable capacitance diodes, and its tunedfrequency is controlled by a tuning voltage supplied to frequencyvariable terminal 64 a.

First input terminal 49 f of mixer 49 connects to output terminal 64 bof double-tuned filter 64, and second input terminal 49 s receivesoutput signals from local oscillator 56 via frequency divider 48. Mixer49 mixes VHF band signals having undergone filter 64 with oscillatingsignals from local oscillator 56, and converts the mixed signals intointermediate frequency signals of 45.75 MHz. Mixer 49 outputs signals tooutput terminal 79 via lead-wire 26, and the output signals are suppliedto intermediate frequency filter 58.

Frequency divider 48 placed approximately at the center of FIG. 2includes divider 48 a for VHF low-band broadcasting and divider 48 b forVHF high-band broadcasting. Switches 67 a, 67 b and 67 c are ones ofmeans for switching the dividers. To be more specific, they switchselectively the oscillating signals from local oscillator 56, the outputsignals from dividers 48 a, 48 b, thereby switching the output signalsto be supplied to mixers 55 and 49.

Local oscillator 56 includes inductor 68, and a series-connected unit ofvariable capacitance diode 69 and capacitor 70. This unit connects toinductor 68 in parallel, thereby forming a tuning section. Theseries-connected unit connects to OSC 71 at its both terminals. OSC 71connects to the tuning section in parallel, and its oscillating signalsare controlled by oscillating frequency changing means connected to OSC71.

The oscillating frequency changing means is formed of capacitors 72, 73,and switches 74 a, 74 b, 77 a, 77 b, connected in parallel with variablecapacitance diode 69.

In this first embodiment, switching of switches 74 a, 74 b, 77 a, 77 ballows changing a capacitance value to be coupled in series tooscillating variable capacitance diode 69 and a capacitance value to becoupled in parallel with diode 69. As a result, a tuned frequency of thetuning section can be changed, so that an oscillating frequency of thelocal oscillator can be minutely controlled.

Variable capacitance diodes can be used instead of switches 74 a, 74 b,77 a, 77 b and capacitors 72, 73, 75, 76. In this case, the diodesreplacing switches 77 a, 77 b and capacitors 72, 73, 75 and 76 canchange their own capacitance in response to a voltage applied thereto,so that an oscillating frequency of the local oscillator can be minutelychanged. Those diodes are referred to as “frequency minutely changingdiode” hereinafter.

Only this case, a voltage control circuit, which controls a voltage tobe supplied to each one of the frequency minutely changing diodes, isneeded. This control circuit changes the voltage to be supplied to thediodes discussed above in response to the supplied data of receivedchannels, thereby changing minutely the oscillating frequency of thelocal oscillator.

Oscillating signals from local oscillator 56 are divided by frequencydivider 48, and then supplied to an input side of PLL circuit 78. PLLcircuit 78 supplies a tuning voltage to variable capacitance diodes 82,84, 86, 89, 96, 98, 102, 107 (shown in FIGS. 3 and 4) of single-tunedfilter 52, double-tuned filter 54, single-tuned filter 62 anddouble-tuned filter 64. It also supplies the tuning voltage tooscillating variable capacitance diode 69.

FIG. 3 shows an actual circuit diagram of single-tuned filter 60 anddouble-tuned filter 54 disposed in UHF signal receiving section 60 inaccordance with the first embodiment. Filter 52 is formed of inductors81, 83, and variable capacitance diodes 82, 84. Frequency variableterminal 52 a is coupled to the cathodes of diodes 82, 84 via resistors.

The tuning voltage supplied from PLL circuit 78 changes the capacitanceof diodes 82, 84 of single-tuned filter 52, so that the tuned frequencycan be controlled. A filter constant of filter 52 is selected such thatthe UHF band signals can pass through filter 52.

Next, double-tuned filter 54 is described hereinafter. Filter 54 isformed of two variable capacitance diodes 86, 89 and two inductors 87,88. Frequency variable terminals 54 a, 54 b are coupled respectively tothe cathodes of diodes 86, 89 via resistors. PLL circuit 78 supplies thetuning voltage from its output side. Filter 54 changes the capacitanceof diodes 86, 89 in response to the tuning voltage supplied to terminals54 a and 54 b, thereby controlling the tuned frequency.

FIG. 4 shows a circuit diagram of single-tuned filter 62 anddouble-tuned filter 64 disposed in VHF signal receiving section 61 inaccordance with the first embodiment. Filter 62 includes inductors 91,92, 93, 94, 97, switch 95, and variable capacitance diodes 96, 98.Frequency variable terminal 62 a is coupled to the cathode of diode 98via resistor 85 b, and receives a tuning voltage from an output side ofPLL circuit 78.

Diodes 96, 98 of single-tuned filter 62 change their capacitance inresponse to the tuning voltage supplied to terminal 62 a, so that thetuned frequency is controlled. A filter constant of filter 62 isselected such that the VHF band signals can pass through filter 62.

Double-tuned filter 64 includes variable capacitance diodes 102, 107,inductors 103, 104, 105, 106, and switch 108. Frequency variableterminal 64 a is coupled to the cathodes of diodes 102, 107 respectivelyvia resistors 85 c, 85 d. Terminal 64 a receives a tuning voltage fromPLL circuit 78. Diodes 102, 107 change their capacitance in response tothe tuning voltage supplied to terminal 64 a of filter 64, so that thetuned frequency can be changed.

In receiving TV broadcastings, an operation of the high-frequencyreceiver in accordance with the first embodiment is demonstrated againhereinafter with reference to FIG. 2. First, when the receiver receivesUHF broadcasting band, switches 74 a, 74 b, 77 a, 77 b are turned off,and switch 67 a is turned on so that frequency divider 48 can supply itsoutput.

When the receiver receives VHF high-band, switches 74 a, 77 a are turnedon, and switches 74 b, 77 b are turned off. Switch 67 b is turned on sothat divider 48 a can supply its output. Switches 95, 108, 109 (shown inFIG. 4) are turned on.

When the receiver receives VHF low-band, switches 74 a, 77 a are turnedoff, and switches 74 b, 77 b are turned on. Switch 67 c is turned on sothat divider 48 b can supply its output. Switches 95, 108, 109 areturned off.

When the receiver receives UHF band, high-frequency amplifier 53 isturned on, and when the receiver receives VHF band, high-frequencyamplifier 63 is turned on. The reason is this: turning off thehigh-frequency amplifier on the non-receiving band side allowsinterrupting high-frequency signals, which have passed through tunedfilter 52 or 62, to mixer 55 or 49. This mechanism allows convertingdesirable high-frequency signals into intermediate frequency signals.

A value of inductor 68 of local oscillator 56 is approx. 20 nH, and thatof capacitor 70 is 22 pF. In this condition, capacitance of variablecapacitance diode 69 is preferably changed between 31 pF and 2.7 pF inresponse to an applied voltage between 2V and 25V. Local oscillator 56thus constructed oscillates signals having frequencies ranging from 350MHz to 850 MHz during the reception of UHF band. It oscillates signalshaving frequencies between 358 MHz and 814 MHz during the reception ofVHF high-band, and between 404 MHz and 692 MHz during the reception ofVHF low-band.

Local oscillator 56 supplies its oscillating signals straightly to mixer55 when the receiver receives UHF band, thereby obtaining intermediatefrequency signals of 45.75 MHz. On the other hand, when the receiverreceives VHF high-band, the oscillating signals from oscillator 56 aredivided their frequencies into ½ by frequency divider 48 a before theyare supplied to mixer 49, so that intermediate frequency signals of45.75 MHz can be obtained.

When the receiver receives VHF low-band of NTSC system broadcasting, theoscillating signals of local oscillator 56 are divided their frequenciesinto ¼ by frequency divider 48 b before the signals are supplied tomixer 49, so that intermediate frequency signals of 45.75 MHz can beobtained. Power supply controller 47 connects to dividers 48 a, 48 b andmixer 49, and turns on or off them in response to an output suppliedfrom image interference determiner 44 to power-supply controllerterminal 47 a.

It is important to set the tuning voltages of single-tuned filters 52,62 and double-tuned filters 54, 64 and the local oscillator for eachchannel at approx. the same value in the respective broadcasting bands.In other words, tuning voltage characteristics of filters 52, 62, 54, 64with respect to each channel are preferably approximated to each otherin the respective broadcasting bands. This preparation is needed inorder to obtain the intermediate frequency signal from mixers 55, 49.For that purpose, tuned-frequencies of single-tuned filters 52, 62 anddouble-tuned filter 54, 64 are tied to each other by local oscillator 56and the frequency dividers, so that high output signals in response tothe intermediate frequencies can be obtained consistently. This is oneof design requirements for high-frequency receivers to receivehigh-frequency signals.

In this first embodiment, switches 74 a, 74 b, 77 a, 77 b switchcapacitors 72, 73, 75, 76, thereby changing minutely capacitance of thetuning section of local oscillator 56, and obtaining local oscillatingfrequency characteristics with respect to the tuning voltages adaptiveto the respective receivable broadcasting bands. The preparationdiscussed above allows the TV broadcasting in the USA to be receivableranging from VHF low-band to UHF band, i.e. all the consecutive channelsfrom 55.25 MHz to 801.25 MHz.

When switching of switches 74 a, 74 b turns on either one of capacitor72 or 73, some capacitance is input in parallel with oscillatingvariable capacitance diode 69. If diode 69 has smaller capacitance thanthis some capacitance, diode 69 cannot contribute so much to theoscillating frequency of oscillator 56. Thus the oscillating frequencyof oscillator 56 at a higher band, where the capacitance of diode 69turns out smaller, can be varied conspicuously.

When switching of switches 77 a, 77 b turns on either one of capacitor75 or 76, some capacitance is input in parallel with capacitor 70. Thispreparation reduces capacitance to be input in series with diode 69, sothat diode 69 can contribute the oscillating frequency of oscillator 56in greater amount, and a range of the oscillating frequency with respectto a tuning voltage can be changed.

Adjustment of the capacitance of capacitors 72, 73, 75, 76 at givenvalues as discussed above allows determining characteristics of channels(frequencies) and tuning voltages in the respective frequency bands,i.e. UHF band, VHF high-band and VHF low-band, independently. Thus thecharacteristics of the tuning voltages at local oscillator 56 withrespect to receivable channels (frequencies) in the respective bands canbe approximated to the characteristics of the tuning voltages of filters52, 62, 54, 64 with respect to receivable channels (frequencies).Further, switches 74, 77 are turned on or off, thereby switchingcapacitors 72, 73, 75, 76 in response to the frequency band to bereceived, so that all the consecutive TV channels in the USA, i.e. fromVHF band to UHF band (55.25 MHz to 801.25 MHz) can be received.

The high-frequency receiver in accordance with the first embodimentemploys oscillating variable capacitance diode 69, variable capacitancediodes 84, 86, 89 (shown in FIG. 3), variable capacitance diodes 98,102, 107 (shown in FIG. 4), all of which have approx. the samecapacitance changing characteristics. As a result, it becomes easier toapproximate the tuned frequency characteristics of single-tuned filters52, 62 or double-tuned filters 54, 64 with respect to the tuning voltageto the tuned frequency characteristics of the tuning section of localoscillator 56 with respect to the tuning voltage.

Oscillating variable capacitance 69, variable capacitance diodes 84, 86,89 (shown in FIG. 3) and variable capacitance diodes 98, 102, 107 (shownin FIG. 4) employ the diodes that have the same capacitance changingrate as that of diode 98, of which capacitance changing rate can changethe tuned frequency of single-tuned filter 62 in response to VHF band.

The reason of employing such diodes is that VHF band, particularly VHFhigh-band, needs the greatest capacitance changing rate. As a result,diodes 69, 84, 86, 89, 98, 102, 107 can employ diodes of the samecharacteristics and the same part-number, so that the part controlbecomes easier. On top of that, mounting wrong parts can be prevented.

Frequency divider 48 and mixer 49 in accordance with the firstembodiment are demonstrated hereinafter with reference to FIG. 5, whichdetails divider 48 and mixer 49. Local oscillator 56 is formed of abalance circuit and outputs signals of phase 0 degree and of phase 180degrees respectively.

Divider 201 for dividing a frequency into ½ (hereinafter referred to ½divider) connects to an output of local oscillator 56, and divides aninput signal into ½ frequency. Divider 201 outputs four signals having aphase difference of 90 degrees from each other. ½ divider 205 connectsto contact 204 b of switch 204. Four output signals from divider 205 aresupplied to respective contacts 67 c of switch 67. Input terminal 205 fof divider 205 receives signals from ½ divider 201, and the signals havea phase difference of 180 degrees from each other, and terminal 205 foutputs four signals having a phase difference of 90 degrees from eachother Mixer 49 is formed of mixer 49 a, 90-degree phase shifter 49 cconnected to mixer 49 a, and mixer 49 b connected in parallel with aseries-connected unit of mixer 49 c and phase-shifter 49 c.

Mixer 49 a connects to output terminal 64 b of double-tuned filter 64 atits first input terminal 49 af, and connects to a common terminal ofswitch 67 at its second input terminal 49 as. On the other hand, mixer49 b connects to output terminal 64 b of filter 64 at its first inputterminal 49 bf, and connects to common terminal 67 k of switch 67 at itssecond input terminal 49 bs. An output from mixer 49 a and an outputsignal from 90-degree phase-shifter 49 c are supplied to output terminal79 (shown in FIG. 2).

The regular operation mode in accordance with the first embodiment isdemonstrated hereinafter. During the reception of UHF band, frequencydividers 201, 205, mixer 49 and phase-shifter 49 c stay turned-off.

During the reception of VHF high-band, switch 204 connects to contact204 a and switch 67 connects to contact 67 b. Divider 201 is turned onwhile divider 205 is turned off. This preparation allows dividing asignal frequency supplied from local oscillator 56 into ½.

During the reception of VHF low-band, switch 204 connects to contact 204b, and switch 67 connects to contact 67 c. This preparation allowsfurther connecting ½ divider 205 between divider 201 and vectorsynthesizers 202, 203. Then divider 205, mixer 49, and phase-shifter 49c are turned on, so that the signal frequency supplied from localoscillator 56 is divided into ¼.

Next, an operation in the power saving mode is demonstrated. During thereception of VHF high-band, mixer 49 b and phase-shifter 49 c are turnedoff additionally to the regular mode operation. Further, switch 204connects to contact 204 a, and switch 67 connects to contact 67 b. Thisstructure allows divider 201 to divide the signal frequency suppliedfrom local oscillator 56 into ½ before the signal is supplied to mixer49 a.

During the reception of VHF low-band, mixer 49 b and phase-shifter 49 care turned off additionally to the regular mode operation. Further,switch 204 connects to contact 204 b and switch 67 connects to contact67 c. This structure allows divider 201 and divider 205 to divide thesignal frequency supplied from local oscillator 56 into ¼ before thesignal is supplied to mixer 49 a.

An operation of frequency dividers 201, 205 shown in FIG. 5 isdemonstrated hereinafter with reference to FIG. 6A, which shows timingcharts of signals in accordance with the first embodiment.

In FIG. 6A, local oscillator 56 outputs signals 1001, 1002 having aphase difference of 180 degrees from each other. Those signals aresupplied to divider 201, which outputs signals 1003, 1004, 1005, 1006having a phase difference of 90 degrees from each other. On the otherhand, divider 205 receives signals 1005, 1006, so that divider 205outputs four signals 1007, 1008, 1009, 1010 having a phase difference of90 degrees from each other.

The foregoing structure allows using the IRM and the DBM by switching,so that the power consumption can be reduced when no image interferenceexists. Mixer 49 thus can work as the DBM, so that a portable receiverconsuming less power is obtainable.

In this first embodiment, ½ frequency dividers 201, 205 are formed offlip-flop circuit, so that a structure of the circuit can be simplified,and use of an integrated circuit will achieve smaller chips. In the caseof obtaining local oscillating signals by dividing the frequencies ofthe oscillating signals supplied from local oscillator 56, divider 48can be a phase-shifter by itself, so that the IRM circuit can bedownsized.

We have discussed that divider 205 receives output signals 1005, 1006;however, divider 205 can receive output signals 1003, 1004 instead. Inthis case, output signals 1011, 1012, 1013, 1014 having a phasedifference of 90 degrees from each other can be obtained. In otherwords, as long as divider 205 receives signals having a phase differenceof 180 degrees, it can outputs four signals having a phase difference of90 degrees from each other.

On top of that, since the IRM can reduce image interference, anattenuating amount of the signals which cause image interference insingle-tuned filter 62 or double-tuned filter 64 can be lowered. Forinstance, filter 64 can be replaced with a low-pass filter during thereception of VHF low-band or VHF high-band. This low-pass filterswitches the cut-off frequencies of the respective bands to the VHFlow-band upper limit frequency or the VHF high-band upper limitfrequency.

Local oscillator 56 changes the oscillating signals in response to aband to be received such that they are tied to the frequencycharacteristics of single-tuned filter 62 or double-tuned filter 64, sothat a range of the oscillating frequency of local oscillator 56 can bebroadened with respect to the tuning voltage. Thus, for instance, ifchannels between UHF band and VHF band are consecutive, those channelscan be received without any problems. As a result, the present inventioncan provide a high frequency receiver which can receive consecutivechannels across the wide band covering VHF and UHF bands of the TVbroadcastings.

Oscillating frequency changing means can change oscillating signals inresponse to a band to be received such that the oscillating signals aretied to the frequency characteristics of filter 62 or filter 64.Therefore, the center frequency of the pass band at filter 62 or filter64 of a desirable channel to be received can be approximated to thefrequency of the desirable channel signals. Filter 62 or filter 64 canthus attenuate undesired interference signals, thereby further reducingimage interference.

In this first embodiment, OSC 71, switches 74, 77, frequency dividers57, 48, mixers 55, 49 and PLL circuit 78 are packed in one integratedcircuit, so that the high-frequency receiver can be downsized.

FIG. 6B shows operations of the respective circuits and statuses of therespective switches during the reception of the respective frequencybands in accordance with this first embodiment. In FIG. 6B, receptionband VL stands for VHF low-band, and VH stands for VHF high-band.

In FIG. 5 and FIG. 6B, when VHF high-band is selected as the band to bereceived, the mixer works as the DBM (double balance mixer) circuit. Atthis time, frequency divider 201 stays turned-on and divider 205 staysturned-off. Mixer 49 a stays turned on, mixers 49 b, 55 stay turned-off.Phase-shifter 49 c stays turned-off. Switch 204 is shut off and staysturned-off, and switch 67 connects to contact 67 c.

In FIG. 5 and FIG. 6B, when VHF low-band is selected as the band to bereceived, the mixer works as the IRM (image rejection mixer) circuit. Atthis time, frequency dividers 201, 205 stay turned-off as they are inthe power-saving mode. Mixers 49 a, 49 b stay turned-on, while mixer 55stays turned-off. Phase-shifter 49 c stays turned-on. Switches 204, 67connect to contacts 204 c, 67 c respectively.

FIG. 6B shows the statuses of respective circuits and switches duringthe reception of respective frequency bands, and those statuses are alsoshown in FIGS. 7B, 9B, 11B and 13B in response to the respectiveembodiments to be discussed later.

Exemplary Embodiment 2

A mixer in accordance with the second embodiment is describedhereinafter with reference to FIG. 7. FIG. 7A shows a block diagram ofthe mixer. In this second embodiment, vector synthesizers 202, 203,limiting circuits 206, 207, and switches 208, 209 are additionallyprovided to the construction of the first embodiment. Switches 208, 209are used as one of mixer input switching means. Elements similar tothose used in the first embodiment have the same reference marks.

In FIG. 7A, switch 67 connects to each one of four outputs fromfrequency divider 201. Switch 67 is connected to vector synthesizers202, 203 at its common terminal 67 k. When switch 67 selects contacts 67b, the output signals from divider 201 connect to vector synthesizer202, so that four output signals are fed into synthesizer 202. Limitingcircuits 206, 207 connect to synthesizers 202, 203 respectively, andthey limit the signals supplied from synthesizers 202, 203 to a givenlevel before the signals are fed into mixers 49 a, 49 b. Switch 208works as the mixer input switching means, and its contact 208 a connectsto an output terminal of limiting circuit 206. Another contact 208 bconnects to common terminal 67 k of switch 67. Switch 208 connects tomixer 49 a at its common terminal 208 k.

Contact 209 a of switch 209 connects to an output terminal of limitingcircuit 207, and contact 209 b connects to common terminal 67 k ofswitch 67, and common terminal 209 k connects to mixer 49 b.

An operation of vector synthesizers 202, 203 in accordance with thesecond embodiment is demonstrated hereinafter. Vector synthesizers 202,203 synthesize the following signals shown in FIG. 6A: a signal of phase0 degree, e.g. output signal 1003 or 1007, a signal of phase 90 degrees,e.g. oscillating signal 1005 or 1009, a signal of phase 180 degrees,e.g. output signal 1004 or 1009, a signal of phase 270 degrees, e.g.output signal 1006 or 1010. In other words, synthesizers 202, 203generate four signals having a phase difference of 90 degrees from eachother.

To be more specific, vector synthesizer 202 generates a signal of phase45 degrees using signals of phase 0 degree and phase 90 degrees. It alsogenerates a signal of phase 225 degrees using signals of phase 180degrees and phase 270 degrees. On the other hand, synthesizer 203generates a signal of phase 135 degrees using signals of phase 90degrees and phase 180 degrees. It also generates a signal of phase 315degrees using signals of phase 0 degree and phase 270 degrees. Thismechanism allows synthesizers 202 and 203 to generate signals having aphase difference of 90 degrees from each other.

Next, an operation of the mixer during the reception of TV broadcastingsin accordance with the second embodiment is detailed hereinafter. First,the operation in the regular mode is demonstrated. During the receptionof VHF high-band in the regular mode, frequency divider 201, vectorsynthesizers 202, 203, limiting circuits 206, 207, mixers 49 a, 49 b andphase-shifter 49 c stay turned-on, while divider 205 stays turned-off.Switch 204 selects contact 204 a, switch 67 selects contact 67 b, switch208 selects contact 208 a, and switch 209 selects contact 209 a. Thisstatus allows vector synthesizers 202, 203 to output signals having aphase difference of 90 degrees from each other and having undergone thedividers where the frequencies of the signals supplied from localoscillator 56 are divided into ½. Those signals are then supplied tomixers 49 a, 49 b, which work as the IRM.

During the reception of VHF low-band, switch 204 selects contact 204 band switch 67 selects contact 67 c. This status allows supplying signalsoutput from local oscillator 56 with their frequencies divided into ¼ tomixers 49 a, 49 b, which work as the IRM. The signals have a phasedifference of 90 degrees from each other.

Next, an operation of the mixer in the power-saving mode is demonstratedhereinafter. During the reception of VHF high-band, vector synthesizers202, 203, limiting circuits 206, 207, mixer 49 b and phase-shifter 49 cstay turned-off. In this status, switch 208 selects contact 208 b, thensignals divided their frequencies into ½ by divider 201 a are suppliedto mixer 49 a. Mixer 49 a works as the DBM, so that lower powerconsumption can be expected.

During the reception of VHF low-band, vector synthesizers 202, 203,limiting circuits 206, 207, mixer 49 b and phase-shifter 49 c are turnedoff. Then switch 208 selects contact 208 b. This status allows frequencydivider 201 to divide the frequencies of the signals into ½, and thosesignals are supplied to mixer 49 a. Mixer 49 a works as the DBM, lowerpower consumption can be expected.

Next, the intermediate mode shown in FIG. 7B will be described. Whenimage interference stays at a low level, it is not necessary to executevector synthesizing. Therefore, switch 209 is disposed between limitingcircuits 207 and mixer 49 b. And, limiting circuit 207 is connected tocontact 209 a of switch 209, and common terminal 67 k of switch 67 isconnected to contact 209 b. Common terminal 209 k of switch 209 isconnected to mixer 49 b. In this way, switch 208 is connected to contact208 b, and also, switch 209 is connected to 209 b, while vectorsynthesizers 202, 203 and limiting circuits 206, 207 are turned off.Accordingly, the intermediate mode of (FIG. 7B) is obtained, and itoperates as IRM the same as in the normal mode in the preferredembodiment 1. In this case, since vector synthesizers 202, 203 andlimiting circuits 206, 207 are not operated, the power consumption canbe more reduced as compared with the normal mode in the preferredembodiment 2.

In this second embodiment, since synthesizers 202, 203 and limitingcircuits 206, 207 are provided, even if frequency dividers 201, 205produce errors in the phases, signals having a phase difference of 90degrees can be positively obtained. Thus signals having an accuratephase are obtainable with respect to such wide-band frequencies as thepresent invention handles, so that signals generating image interferencecan be largely suppressed.

FIG. 7B shows relations between the respective circuits and statuses ofthe switches in each mode. In FIG. 7B, receivable band “VL” stands forVHF low-band, and “VH” stands for VHF high-band. The way of reading thestatuses of the switches is the same as that shown in FIG. 6B describedin the first embodiment, so that detailed description is omitted here.

Exemplary Embodiment 3

The third exemplary embodiment is described hereinafter with referenceto FIG. 8, which shows a block diagram of a high-frequency receiver inaccordance with the third embodiment. Elements similar to those used inFIG. 2 described in the first embodiment have the same reference markshere.

Oscillator 356 placed approx. at the center of FIG. 8 oscillates signalshaving frequencies ranging from 700 MHz to 1700 MHz. In other words,oscillator 356 is a local oscillator having frequencies twice as much asthat of the first embodiment. Those oscillating frequencies aredetermined by inductor 368 and variable capacitance diode 369, and thecapacitance of respective capacitors 372, 373, 375, and 376 are adjustedat given values. For the respective receivable bands, changingcharacteristics of single-tuned filters 52, 62, double-tuned filter 54,64 and local oscillator 356 with respect to tuning voltages areapproximated to each other so that the difference between the frequencyof local oscillator 356 and passing frequencies of filters 52, 62, 54,64 can become approx. equal to the intermediate frequency (45.75 MHz).

In this third embodiment, mixer 355 employs IRM, frequency divider 366 adivides frequencies into ¼, and divider 366 b divides frequencies into⅛. Divider 357 and switch 67 a are connected between local oscillator356 and mixer 355. Mixers 355, 365 connect to output terminal 79 attheir output sides. Output signals taken out from output terminal 79 aresupplied to intermediate frequency filter 58. Mixer 355 is used duringthe reception of UHF band, and mixer 365 is used during the reception ofVHF high-band.

Mixer power supply controller 383 connects to divider 366, and mixers355, 365. Control terminal 388 a of controller 383 receives controlsignals supplied from image interference determiner 44 (shown in FIG.1). Parts of the circuits of divider 366, mixer 355 or 365 are turned onor off in response to the control signals.

Next, operations of frequency dividers 357, 366, and mixers 355 a, 355b, 365 a, 365 b with reference to FIG. 9A are demonstrated hereinafter.FIG. 9A shows a detailed block diagram illustrating frequency dividersand mixers in accordance with the third embodiment. Elements similar tothose used in FIGS. 2, 5, and 7A have the same reference marks, and thedescriptions thereof are simplified here.

Mixer 355 a connects to output terminal 54 b of double-tuned filter 54at its first input terminal 355 af, and connects to an output terminalof limiting circuit 206 at its second input terminal 355 as. Mixer 355 bconnects to 90-degree phase shifter 355 c at its output side. Mixer 355b and phase-shifter 355 c form a series-connected unit, which isconnected in parallel with mixer 355 a. Mixer 355 a and phase-shifter355 c supply their output signals to output terminal 79.

On the other hand, in FIG. 9A, mixer 365 a connects to output terminal64 b of double-tuned filter 64 at its first input terminal 365 af, andconnects to an output terminal of limiting circuit 206 at its secondinput terminal 365 as.

Mixer 365 a is connected in parallel with the series-connected unit ofmixer 365 b and phase-shifter 365 c. Mixer 365 a and phase shifter 365 csupply their output signals to output terminal 79. Mixer 365 b connectsto output terminal 64 b of double-tuned filter 64 at its first inputterminal 365 bf, and connects to an output terminal of limiting circuit207 at its second input terminal 365 bs. Mixer 365 b connects to90-degree phase shifter 365 c at its output terminal.

Switch 67 switches three input signals, and connects to vectorsynthesizers 202, 203 at its common terminal 67 k. Between contact 67 aof switch 67 and local oscillator 356, ½ frequency divider 402 isconnected. Divider 402 divides frequencies of signals supplied fromlocal oscillator 356 into ½, and outputs four signals having a phasedifference of 90 degrees from each other.

Frequency divider 402 connects to a common terminal of switch 401 at itstwo output terminals 402 c, and contact 401 a of switch 401 connects tocontact 67 a of switch 67, and contact 401 b connects to an inputterminal of ½ frequency divider 201. Divider 402 outputs four signalshaving a phase of 0 degree, 90 degrees, 180 degrees and 270 degreesrespectively. Signals supplied to divider 201 may have a phasedifference of 180 degrees, so that two signals from divider 402 can beused since the two signals have a phase of 90 degrees and a phase of 270degrees.

In FIG. 9A, switches 403 are connected respectively between twoterminals selected from among common terminals 67 k of switch 67 andinput terminals of mixers 355 a and 365 a. Switch 403 switches supplyingsignals from switch 67 to synthesizers 202, 203 to supplying the signalsto mixers 355 a, 365 a.

In the foregoing structure, an operation of the mixer during thereception of TV broadcastings is demonstrated hereinafter. First, theoperation in the regular mode is demonstrated.

In the case of receiving UHF band, switch 401 selects contact 401 a, andswitch 67 selects contact 67 a. Then switch 403 selects contact 403 a,so that vector synthesizers 202, 203 receive signals of whichfrequencies are reduced to ½ from those of the original signals suppliedfrom local oscillator 356. Mixer 365 and phase-shifter 365 c stayturned-off because they are the mixers for receiving VHF band, andfrequency dividers 201, 205 also stay turned-off. Circuits other thanthose discussed above are turned-on. This structure allows supplyingsignals having a phase difference of 90 degrees from each other tomixers 355 a, 355 b. Those signals have been supplied from localoscillator 56 and their frequencies have been divided into ½ by divider402. Mixers 355 a, 355 b thus work as the IRM.

Next, in the case of receiving VHF high-band, switch 401 selects contact401 b, and switch 67 selects contact 67 b. Then switch 204 selectscontact 204 a. Switch 403 selects contact 403 a, so that ½ frequencydivider 402 is connected to ½ frequency divider 201. Since mixer 355 andphase-shifter 355 c are exclusively used for receiving UHF band, theyare turned off. Divider 205 is also turned off. This structure allowssupplying signals having a phase difference of 90 degrees from eachother to mixers 365 a, 365 b. Frequencies of those signals have beendivided into ¼ from the original ones supplied from local oscillator356. Mixers 365 a, 365 b thus work as the IRM.

In the case of receiving VHF low-band, switch 401 selects contact 401 b,and switch 67 selects contact 67 c. Then switch 204 selects contact 204b and switch 403 selects contact 403 a. Since mixer 355 a, 355 b andphase-shifter 355 c are exclusively used for receiving UHF band, theyare turned off. In other words, three ½ frequency dividers 402, 201, 205are formed between local oscillator 356 and vector synthesizers 202,203. This structure allows supplying signals having a phase differenceof 90 degrees from each other to mixers 365 a, 365 b. Frequencies ofthose signals have been divided into ⅛ from the original ones suppliedfrom local oscillator 356. Mixers 365 a, 365 b thus work as the IRM.

In the case of receiving TV broadcastings in the power-saving mode,there are several points different from the reception in the regularmode: First, during the reception of VHF band, vector synthesizers 202,203, limiting circuits 206, 207, mixer 355 b and phase-shifter 355 cstay turned-off. Further, switch 403 selects contact 403 b, thenoscillating signals from local oscillator 356 are divided theirfrequencies into ½ by frequency divider 402, which supplies signalshaving a phase difference of 180 degrees from each other to mixer 355bypassing synthesizer 202 and limiting circuit 206. Mixer 365 a thusworks as the DBM.

During the reception of VHF high-band, vector synthesizers 202, 203,limiting circuits 206, 207, mixer 365 b and phase-shifter 365 c areturned off. Further, switch 403 selects contact 403 b, then oscillatingsignals from local oscillator 356 are divided their frequencies into ¼by frequency dividers 402 b, 201. Divider 201 supplies signals having aphase difference of 180 degrees from each other to mixer 365 a bypassingsynthesizer 202 and limiting circuit 206. Mixer 365 a thus works as theDBM.

During the reception of VHF low-band, vector synthesizers 202, 203,limiting circuits 206, 207, and phase-shifter 365 c stay turned off.Further, switch 403 selects contact 403 b, then oscillating signals fromlocal oscillator 356 are divided their frequencies into ⅛ by frequencydividers 402 b, 201 b, 205 a.

Divider 205 a supplies signals having a phase difference of 180 degreesfrom each other to mixer 365 a bypassing synthesizer 202 and limitingcircuit 206. Mixer 365 a thus works as the DBM.

The foregoing structures allow the mixer to work as the DBM in thepower-saving mode, so that the high-frequency receiver can be expectedto consume less power.

On top of that, during the reception in the regular mode, four signalshaving a phase difference of 90 degrees from each other are supplied tovector synthesizers 202, 203 regardless of frequency bands to bereceived. When UHF band is received, desirable signals to be receivedand output signals from synthesizers 202, 203 are mixed by mixers 355 a,355 b and 90-degree phase-shifter 355 c. Thus the UHF signal receivingsection works as the IRM, so that image interference can be reduced evenduring the reception of UHF broadcastings.

Since the IRM can reduce image interference, single-tuned filter 52 anddouble-tuned filter 54 can moderate attenuating the signals which causeimage interference. Meanwhile, a high-pass filter, which passes signalsover UHF band, can be used instead of double-tuned filter 54.

Synthesizing of vectors allows correcting errors possibly found inoutput signals from dividers 402, 201, and 205, so that signals havingaccurate phase difference of 90 degrees from each other are obtainableacross wide range frequencies. Thus a high-frequency receiver highlyresistant to interference during the reception of UHF band isachievable.

FIG. 9B shows relations between the respective circuits and statuses ofthe switches in each mode during the reception of the respectivebroadcasting bands. In FIG. 9B, receivable band “VL” stands for VHFlow-band, and “VH” stands for VHF high-band. The way of reading thestatuses of the switches is the same as that shown in FIG. 6B describedin the first embodiment, so that detailed description is omitted here.

Exemplary Embodiment 4

The fourth embodiment uses the IRM for VHF high-band and a harmonicrejection mixer (HRM) for VHF low-band in the circuits of VHF signalreceiving section 61 used in the first embodiment.

FIG. 10 shows a block diagram of a high-frequency receiver in accordancewith the fourth embodiment. In FIG. 10, similar elements to those usedin FIG. 2 have the same reference marks, and the descriptions thereofare simplified. In FIG. 10, input terminal 51 receives high-frequencysignals having frequencies between 55.25 MHz and 801.25 MHz. UHF signalreceiving section 560 is formed of single-tuned filter 52,high-frequency amplifier 53, double-tuned filter 54, and mixer 55.

VHF signal receiving section 561 receives VHF band signals from amongthe signals supplied to input terminal 51, where the VHF band signalshave frequencies ranging from 55.25 MHz to 361.25 MHz. VHF signalreceiving section 561 is formed of single-tuned filter 62,high-frequency amplifier 63, low-pass filter 564 and mixer 565 connectedin this order.

Low-pass filter 564 receives output signals from high-frequencyamplifier 63, and passes VHF band signals having the frequencies nothigher than 361.25 MHz.

Mixer 565 connects to output terminal 564 a of low-pass filter at itsfirst input terminal, and connects to an output terminal of localoscillator 56 via frequency divider 566 at its second input terminal.Mixer 565 mixes the VHF band signals having undergone low-pass filter564 with the oscillating signals from local oscillator 56, and convertsthe mixed signals into intermediate frequency signals (45.75 MHz). Theoutput signals from mixer 565 are supplied to an input terminal ofintermediate frequency filter 58 via output terminal 79.

Frequency divider 566 includes frequency divider 566 b for VHF low-bandsignals and divider 566 a for VHF high-band signals. Switch 67selectively switches to or from the output signals supplied fromoscillator 56, the output signals supplied from dividers 566 a, 566 bbefore those signals are supplied to mixer 565.

Power supply control circuit 567 includes control terminal 567 a, whichreceives output signals from image interference determiner 44 (shown inFIG. 1), so that control circuit 567 turns on or off a part of divider566 or a part of mixer 565 in response to control signals supplied fromdeterminer 44.

Next, the reception of TV broadcastings by the high-frequency receiverin accordance with the fourth embodiment is described hereinafter. Sincethe UHF band receiving section is the same as that of the firstembodiment, the receptions of VHF high-band and VHF low-band aredescribed here.

Local oscillator 56 oscillates signals having frequencies ranging from358 MHz to 814 MHz during the reception of VHF high-band, and oscillatessignals having frequencies ranging from 404 MHz to 692 MHz during thereception of VHF low-band.

During the reception of VHF high-band, oscillating signals from localoscillator 56 are divided their frequencies by divider 566 a before theyare supplied to mixer 565, so that intermediate frequency signals of45.75 MHz are produced. In NTSC broadcasting system, during thereception of VHF low-band, the oscillating signals from oscillator 56are divided their frequencies into ¼ by divider 566 b before thosesignals are supplied to mixer 565, so that intermediate frequencysignals of 45.75 MHz are produced.

Next, frequency divider 566 and mixer 565 are described with referenceto FIG. 11A, which details divider 566 and mixer 565. (150) In FIG. 11A,elements similar to those in FIG. 5 have the same reference marks, andthe descriptions thereof are simplified here. Mixer 565 connects tomixer 49 a, mixer 49 b connects in parallel to mixer 49 a, and 90-degreephase-shifter 49 c connects to an output side of mixer 49 b. A firstinput terminal of mixer 49 a connects to output terminal 564 a oflow-pass filter 564, and a second input terminal of mixer 49 a receivesoutput signals from limiting circuit 206. On the other hand, first inputterminal 49 bf of mixer 49 b connects to output terminal 564 a oflow-pass filter 564, and second input terminal 49 bs connects to anoutput terminal of limiting circuit 207.

Common terminal 67 k of switch 67 connects to output terminals 201 c,201 d of ½ frequency divider 201, and contact 67 d of switch 67 connectsto vector synthesizers 202, 203.

Contact 67 c of switch 67 connects to ½ frequency dividers 601, 602,which divide the frequencies of signals supplied from divider 201 into ½. Divider 201 supplies four signals having a phase difference of 90degrees from each other. Divider 601 receives signals having a phasedifference of 180 degrees from each other via switch 67, where thosesignals have undergone divider 201. On the other hand, divider 602receives signals having a phase difference of 180 degrees from eachother via switch 67, where those signals have undergone divider 201.

Vector synthesizers 603, 604 receive four signals from divider 601,where these signals have a phase difference of 90 degrees from eachother, and synthesizes the vectors of these signals. ½ vectorsynthesizers 605, 606 receive four signals from divider 602, where thesesignals have a phase difference of 90 degrees from each other, andsynthesizes the vectors of these signals.

Limiting circuit 607, 608, 609, and 610 receive output signals fromvector synthesizers 603, 604, 605, and 606 respectively. Mixers 565 d,565 f, 565 h, and 565 j receive output signals from limiting circuits607, 608, 609, and 610 at their first input terminals respectively, andconnect to output terminals 564 a at their second input terminals.

Mixer 565 d connects to 135-degree phase shifter 565 e at its outputterminal, mixer 565 f connects to 45-degree phase shifter 565 g at itsoutput terminal, mixer 565 h connects to 90-degree phase shifter 565 iat its output terminal. Those four mixers supply signals to outputterminal 79.

In this fourth embodiment, switch 611 is provided, so that frequencydivider 201 outputs signals straightly to mixer 49 a bypassing vectorsynthesizer 202 and limiting circuit 206. Switch 612 is provided, sothat frequency divider 602 outputs signals straightly to mixer 565 jbypassing vector synthesizer 606 and limiting circuit 610.

An operation during the reception of TV broadcastings is demonstratedhereinafter. During the reception of VHF high-band in the regular mode,switch 67 selects contact 67 d, and switch 611 is turned off. Further,divider 201, synthesizers 202, 203, and limiting circuits 206, 207 areturned on, while the circuits other than foregoing ones are turned off.This structure allows divider 201 to divide the frequency of localoscillator 56 into ½, then oscillator 56 outputs signals having a phasedifference of 90 degrees from each other. Those signals are supplied tomixers 49 a, 49 b via synthesizers 202, 203 and limiting circuits 206,207. The mixers thus work as the IRM.

During the reception of VHF low-band, switch 67 selects contact 67 e,and switch 612 is turned off. Further, dividers 201, 602, synthesizers605, 606, and limiting circuits 609, 610, mixers 565 h, 565 j, and phaseshifter 565 i are turned on, while the circuits other than foregoingones are turned off. This structure allows dividers 201, 602 to dividethe frequency supplied from local oscillator 56 into ¼, then divider 602outputs signals having a phase difference of 180 degrees from eachother. The signals having a phase difference of 90 degrees from eachother are supplied to mixers 565 h, 565 j via synthesizers 605, 606 andlimiting circuits 609, 610. The mixers thus work as the IRM.

An operation during the reception of TV broadcastings in thepower-saving mode is demonstrated hereinafter. During the reception ofVHF high-band, switch 67 selects contact 67 d, and switch 611 is turnedon. Further, synthesizers 202, 203, and limiting circuits 206, 207,mixer 49 b and phase shifter 49 c are turned off. This structure allowsdivider 201 to divide the frequency supplied from local oscillator 56into ½, then oscillator 56 outputs signals having a phase difference of90 degrees from each other straightly to mixer 49 d bypassingsynthesizer 202 and limiting circuit 206. The mixer thus works as theDBM.

On the other hand, during the reception of VHF low-band, switch 612 isturned on, and vector synthesizers 605, 606, limiting circuits 609, 610,mixer 565 h and phase shifter 565 i are turned off. This structureallows divider 602 b to output signals straightly to mixer 565 jbypassing synthesizer 606 and limiting circuit 610, so that the mixerworks as the DBM.

On top of that, during the reception of VHF low-band, the mode isswitched to a high-quality mode where the mixer works as the HRM(harmonic rejection mixer). In the high-quality mode, switch 67 selectscontact 67 e, and switch 612 is turned off. Further, synthesizers 202,203, and limiting circuits 206, 207, mixers 49 a, 49 b, and phaseshifter 49 c are turned off, while the circuits other than foregoingones are turned on. This structure allows dividers 201, 601, 201, 602 todivide the frequencies of oscillating signals supplied from localoscillator 56 into ¼, then dividers 601, 602 respectively output foursignals having a phase difference of 45 degrees from each other. Thesignals are supplied to mixers 565 d, 565 f, 565 h, 565 j viasynthesizers 603, 604, 605, 606 and limiting circuits 607, 608, 609,610. The mixers thus work as the HRM.

As discussed above, during the reception of VHF low-band, the mixer canselect the way of working from among the HRM, IRM, and DBM. During thereception of VHF high-band, the mixer can select the way of workingbetween the IRM and DBM. This mechanism allows the mixer to work as theDBM when no image interference exists, so that the high-frequencyreceiver can be expected to consume less power, and the portable deviceusing the same receiver also consumes less power.

An operation of frequency dividers 201, 601, 602 and vector synthesizers202, 203, 603, 604, 605, 606 in accordance with the fourth embodiment isdemonstrated hereinafter with reference to FIG. 12, which shows thetiming charts of dividers 601, 602. Elements similar to those used inFIG. 6 have the same reference marks, and the descriptions thereof aresimplified here.

Frequency divider 201 outputs signals 1003, 1004, 1005, and 1006. Signal1003 has a phase of 0 degree, and signals 1004, 1005, 1006 has a phasedifference of 180, 90, and 270 degrees respectively from the phase ofsignal 1003.

Frequency divider 601 outputs signals 1021, 1022, 1023, and 1024. Signal1021 has a phase of 0 degree, which is the same as that of signal 1003,so that those two signals has a phase difference of 0 degree. Signals1022, 1023, 1024 has a phase difference of 90, 180, and 270 degreesrespectively from the phase of signal 1021.

Frequency divider 602 outputs signals 1025, 1026, 1027 and 1028. Signal1025 has a phase difference of 45 degrees from signals 1003 and 1021.

-   -   Phases of signals 1026, 1027, and 1028 are shifted 135, 225, and        315 degrees from each other.

The structure discussed above allows dividing the oscillating signalssupplied from local oscillator 56 into given frequencies, and allowssynthesizers 603, 604, 605 and 606 to output eight signals 1021, 1025,1022, 1026, 1023, 1027, 1024 and 1028 having a phase difference of 45degrees from each other. In other words, vector synthesizer 603synthesizes output signal 1022 having a phase of 90 degrees and outputsignal 1023 having a phase of 180 degrees, thereby producing an outputsignal having a phase of 135 degrees. It also synthesizes output signal1021 having a phase of 0 degree and output signal 1024 having a phase of270 degrees, thereby producing an output signal having a phase of 315degrees.

On the other hand, vector synthesizer 604 synthesizes output signal 1021having a phase of 0 degree and output signal 1022 having a phase of 90degrees, thereby producing an output signal having a phase of 45degrees. It also synthesizes output signal 1023 having a phase of 180degrees and output signal 1024 having a phase of 270 degrees, therebyproducing an output signal having a phase of 225 degrees.

Vector synthesizer 605 synthesizes output signal 1025 having a phase of45 degrees and output signal 1026 having a phase of 135 degrees, therebyproducing an output signal having a phase of 90 degrees. It alsosynthesizes output signal 1027 having a phase of 225 degrees and outputsignal 1028 having a phase of 315 degrees, thereby producing an outputsignal having a phase of 270 degrees. Vector synthesizer 606 synthesizesoutput signal 1025 having a phase of 45 degrees and output signal 1028having a phase of 315 degrees, thereby producing an output signal havinga phase of 0 degree. It also synthesizes output signal 1026 having aphase of 135 degrees and output signal 1027 having a phase of 225degrees, thereby producing an output signal having a phase of 180degrees.

The structure discussed above allows frequency dividers 201, 601 and 602to have a function of frequency divider which divides a frequency of asignal having a given frequency and also have a function ofphase-shifter. Mixers 49 a and 49 b thus form the IRM during thereception of VHF high-band, and mixers 565 d, 565 f, 565 h and 565 jform the HRM during the reception of VHF low-band. As a result, imageinterference can be reduced during the reception of VHF high-band, andhigher local harmonic interference can be reduced during the receptionof VHF low-band. This reduction of higher local harmonic interference isdisclosed by the same inventors in Japanese Patent UnexaminedPublication No. 2004-179841. Meanwhile the HRM in accordance with thefourth embodiment is formed of four mixers, so that interference due toharmonics of not higher than five times of the output signal fromdivider 566 b can be reduced during the reception of VHF high-band.

In the receiver equipped with a local oscillator and a frequencydivider, a divider for VHF low-band has a smaller dividing rate than adivider for VHF high-band, so that the IRM can be formed during thereception of VHF high-band, and the HRM can be formed during thereception of VHF low-band where higher-order harmonic interference canbe possibly generated.

Since the IRM and the HRM can reduce image interference and localharmonic interference, low-pass filter 564 can use a low-pass filter. Ontop of that, forming of the HRM for VHF low-band allows reducing adverseinfluence from VHF high-band signals which interferes with the receptiontogether with local harmonics. Thus a tuned filter is not needed for VHFlow-band, and VHF low-pass filter 564 proper to the receiver can workenough, so that the cost of the high-frequency receiver can be reduced.Since VHF low-pass filter 564 is proper to the receiver, desirablesignals can undergo this filter with less passing loss. As a result, ahigh-frequency receiver with better C/N is achievable.

In this fourth embodiment, ½ frequency dividers 201, 601, and 602 areformed of flip-flop circuits, which simplify the circuit structure, sothat use of an integrated circuit will increase a packing density.

Since vector synthesizers 202, 203, 603, 604, 605 and 606 are provided,signals having different phases can be accurately obtained even iferrors are produced in the output signals from dividers 201, 601 and602. Signals having accurate phases are thus obtainable across thewide-band frequencies such as VHF band, so that image interference andlocal harmonics interference can be steadily suppressed.

OSC 71, switches 74, 77, frequency divider 566, mixers 55, 565 and PLLcircuit 78 are packaged into one integrated circuit, so that thehigh-frequency receiver can be downsized.

FIG. 11B shows relations between operations of the respective circuitsand statuses of the switches in accordance with the fourth embodiment.In FIG. 11B, receivable band “VL” stands for VHF low-band, and “VH”stands for VHF high-band. The way of reading the statuses of theswitches shown in FIG. 11B is the same as that shown in FIG. 6Bdescribed in the first embodiment, so that detailed description isomitted here.

Exemplary Embodiment 5

The high-frequency receiver in accordance with the fifth embodimentworks as the HRM during the reception of VHF low-band, while it works asthe IRM during the reception of VHF high-band using parts of the HRM.Thus the receiver can share parts of its mixing circuits, so that thecircuits can be downsized and the cost thereof can be lowered.

FIG. 13A shows a block diagram illustrating frequency dividers andmixers in accordance with the fifth embodiment. Elements similar tothose used in FIGS. 5, 9, and 10 have the same reference marks, and thedescriptions thereof are simplified here.

In this fifth embodiment, switch 701 is connected between output 201 cof ½ frequency divider 201 and contact 67 b of switch 67 with respect tothe IRM shown in FIG. 7A described in the second embodiment. Switch 701receives an output from divider 201 at its common terminal. Contact 701a of switch 701 connects to contact 67 b of switch 67.

Switch 208 connected between limiting circuit 206 and mixer 49 a isreplaced with switch 704, which is specifically disposed between commonterminal 67 k of switch 67 and mixer 49 a. Dividers 201, 205 supplysignals to mixers 49 a, 49 b via vector synthesizers 202, 203, andlimiting circuits 206 and 207, while an output from contacts 701 b ofswitch 701 is supplied to ½ frequency divider 601.

Both in the regular mode and the power-saving mode, the receptions ofVHF high-band and low-band are substantially the same as those in thesecond embodiment, only switch 704 selects contact 704 a in the regularmode and selects contact 704 b in the power-saving mode.

The structure discussed above allows mixers 49 a, 49 b to work as theIRM in the regular mode, and to work as the DBM in the power-savingmode, so that the portable receiver consuming less power is achievable.

On top of that, the high-quality mode is available in the fifthembodiment as it is available in the fourth embodiment. During thereception of VHF low-band, switch 701 selects contact 701 b, switch 204selects contact 204 b, switch 67 selects contact 67 c, and switch 704selects contact 704 a. This structure allows frequency signals suppliedfrom local oscillator 56 to be divided into ¼ by dividers 201, 205, anddividers 201, 601, so that dividers 205 and 601 supply signals having aphase difference of 90 degrees from each other to mixers 565 d, 565 fvia vector synthesizers 603, 604 and limiting circuits 607, 608. Themixers thus work as the HRM.

FIG. 13B shows relations between operations of the respective circuitsand statuses of the switches in accordance with the fifth embodiment.The way of reading the statuses of the switches shown in FIG. 13B is thesame as that shown in FIG. 6B described in the first embodiment, so thatdetailed description is omitted here.

As discussed above, the high-frequency receiver and the portable deviceusing the same receiver in accordance with the fifth embodiment can workas the HRM during the reception of VHF low-band, while they can work asthe IRM during the reception of VHF high-band, so that mixer 49 can becommonly used for the entire VHF band. As a result, the circuits becomesmaller, and the high-frequency receiver can be downsized.

INDUSTRIAL APPLICABILITY

A high-frequency receiver and a portable device using the same receiverof the present invention changes the structure of their mixers inresponse to existence of image interference signals, so that less powerconsumption can be expected. The receiver is thus useful in anelectronic tuner for receiving TV broadcastings carrying wide-bandsignals, so that the receiver is highly applicable to the industrialuse.

1. A high-frequency receiver comprising: (a) a high-frequency signalinput terminal for receiving high-frequency signals; (b) a tuned filtercoupled to the input terminal; (c) a first mixer including a doublebalance mixer circuit having a first input terminal which receives anoutput signal from the tuned filter and a second input terminal whichreceives an output signal from a local oscillator; (d) an outputterminal for receiving an output signal from the first mixer; (e) asecond mixer connected between the tuned filter and the output terminal,and having an image rejection mixer circuit which receives an outputfrom the local oscillator; (f) a power supply control circuit coupled tothe image rejection mixer circuit and controlling a power supply whichpowers the image rejection mixer circuit; (g) an image interferencedeterminer coupled to an input side of the power supply control circuit;and (h) a phase locked loop (PLL) circuit coupled to the localoscillator, wherein the image interference determiner determines whetheror not image interference exists at a present position with respect to achannel desirable to be received, and the power supply control circuitallows the first mixer to work as the double balance mixer when thedeterminer determines no image interference exists.
 2. Thehigh-frequency receiver of claim 1, wherein at least one of the mixersthat include the image rejection mixer circuits shares a mixer whichincludes the double balance mixer circuit.
 3. The high-frequencyreceiver of claim 1, wherein the image rejection mixer circuit includes:a local oscillator for outputting signals having a phase difference of180 degrees from each other; a first frequency divider coupled to anoutput of the local oscillator and outputting four signals having aphase difference of 90 degrees from each other; a first vectorsynthesizer for receiving an output signal from the first divider, andsynthesizing the output signals supplied from the first divider tooutput signals having a phase difference of 180 degrees from each other;a first mixer for receiving an output from the first synthesizer at itsfirst input terminal, and receiving the high-frequency signal at itssecond input terminal; a second vector synthesizer for receiving theoutput signal from the first divider and synthesizing the output signalssupplied from the first divider to output a signal having a phasedifference of 90 degrees from the output signal supplied from the firstvector synthesizer; a second mixer for receiving the output signal fromthe second vector synthesizer at its first input terminal, and receivingthe high-frequency signal at its second input terminal; a phase shifterconnected between an output signal and an output terminal either one ofthe first mixer and the second mixer; and a mixer input switching meansprovided between either one of the first and second dividers and eitherone of the first and second mixers such that the either one of thedivider outputs a signal to either one of the mixers bypassing eitherone of the first and second vector synthesizers, wherein when the imageinterference determiner determines that image interference happens in areceived channel, the switching means supplies the output signal fromthe divider to the first mixer bypassing the first vector synthesizer,and the power supply control circuit turns off at least one of the firstvector synthesizer and the first mixer.
 4. The high-frequency receiverof claim 1 further comprising a frequency switching means connectedbetween a first frequency divider and a first vector synthesizer, andbetween the first frequency divider and a second vector synthesizer,wherein the frequency synthesizer includes: a second frequency dividerfor receiving two output signals having a phase difference of 180degrees from each other supplied from the first frequency divider; and adivider switching means for selectively supplying an output signal fromthe first divider and the second divider to the first vector synthesizerand the second vector synthesizer, wherein the second frequency divideroutputs four signals having a phase difference of 90 degrees from eachother, and the high-frequency signal includes a first frequency bandbroadcasting signal and a second frequency band broadcasting signal ofwhich frequency is higher than the first frequency band, and the dividerswitching means supplies an output from the second divider to the firstand the second mixers during a reception of the first frequency bandbroadcasting signal, and the divider switching means supplies an outputfrom the first divider to the first and the second mixers and also turnsoff the second divider during a reception of the second frequency bandbroadcasting signal.
 5. A portable device comprising: a high-frequencyreceiver including: (a) a high-frequency signal input terminal forreceiving high-frequency signals; (b) a tuned filter coupled to theinput terminal; (c) a first mixer including a double balance mixercircuit having a first input terminal which receives an output signalfrom the tuned filter and a second input terminal which receives anoutput signal from a local oscillator; (d) an output terminal forreceiving an output signal from the first mixer; (e) a second mixerconnected between the tuned filter and the output terminal, and havingan image rejection mixer circuit which receives an output from the localoscillator; (f) a power supply control circuit coupled to the imagerejection mixer circuit and controlling a power supply which powers theimage rejection mixer circuit; (g) an image interference determinercoupled to an input side of the power supply control circuit; and (h) aphase locked loop (PLL) circuit coupled to the local oscillator, whereinthe image interference determiner determines whether or not imageinterference exists at a present position with respect to a channeldesirable to be received, and the power supply control circuit allowsthe first mixer to work as the double balance mixer when the determinerdetermines no image interference exists, a position data obtaining meanscoupled to an antenna and obtaining data of a present position; a signalprocessor for receiving an output from the high-frequency receiver; anda display and an audio output device to which an output signal issupplied from the signal processor, wherein the image interferencedeterminer receives an output signal from the position data obtainingmeans at its first input terminal, and connects to a memory at itssecond input terminal, and the memory stores a plurality of receivablefrequencies corresponding to the position data, wherein the imageinterference determiner determines, in response to the position dataobtained from the position data obtaining means, whether or not areceived channel involves image interference, and when the determinerdetermines no image interference happens in the received channel, thedeterminer turns off an image rejection mixer circuits of the mixer, andswitches the mixer to a double balance mixer circuit.